IOS11 WebView for "Add to home screen" button

After iOS11 upgrade, what WebView (WebKit) is used for "Add to home screen" button from Safari (used to see apps in fullscreen)?
I know that in iOS 10, it was using UIWebView.

Is it an upgrade for UIWebView or is it replaced with WKWebView?

I saw that in iOS 11, I don't have the problem with the 300 ms delay, but I have some problems with the orientation change.

Thank you

Solution

Based on the JavaScript test of this answer, Web Apps are getting displayed in a WKWebView in iOS 11.

You can also validate this with the following code snippet:

function browserTest() {
  var whatBrowser = document.getElementById("whatBrowser");
  var lte9 = /Constructor/i.test(window.HTMLElement);
  var nav = window.navigator, ua = nav.userAgent, idb = !!window.indexedDB;
  var browserText = "Other Browser"; 

  if (ua.indexOf('Safari') !== -1 && ua.indexOf('Version') !== -1 && !nav.standalone) { 
    browserText = "Safari";
  } else if ((!idb && lte9) || !window.statusbar.visible) {
    browserText = "UIWebView";
  } else if ((window.webkit && window.webkit.messageHandlers) || !lte9 || idb) {
    browserText = "WKWebView";
  }
  
  whatBrowser.innerHTML = browserText;
}

<html>
  <head>
    <meta name="apple-mobile-web-app-capable" content="yes">
  </head>
  <body onload="browserTest();">
    <p id="whatBrowser"></p>
  </body>
</html>